Modern surfboards desirably include a fin adjacent the tail thereof, and along the centerline of the board, to provide dimensional stability, to maximize board performance. While conventional fins are certainly useful for that purpose, they pose two significant problems. One is that the fin can be dangerous to surfers or nearby swimmers if the surfboard is travelling at high speed and the leading or trailing edge of the fin hits the surfer or swimmer. Also, while providing good dimensional stability, a fin may, depending upon the circumstances, restrict maneuverability.
According to the invention in the parent application a surfboard fin, and a surfboard, are provided which overcome the problems inherent in the prior art. According to the most basic aspects thereof, a surfboard fin or fins are provided which have soft, flexible leading and trailing edges so that if they impact a surfer or swimmer the injury will be minimized. The flexible material at the trailing edge of the fin or fins also provides a rudder action to provide maneuverability to a surfer standing on the top surface of the board and shifting his/her weight. Although numerous advantages are obtained by utilizing a single tail fin, preferably a plurality of fins are provided, e.g. three fins spaced at particular locations adjacent the tail of the board.
According to one aspect of the invention of the parent application a surfboard tail fin is provided comprising: A rigid body element having a leading edge, and a trailing edge; and a flexible material covering disposed on the leading and trailing edges of the rigid body element. The flexible material is soft enough to minimize injury to a person impacted by a leading or trailing edge of the fin, and is flexible enough to be deflected by water pressure during surfing to provide a rudder action. Preferably the rigid body element is of a hard plastic having a Shore D hardness of at least about 60 (and preferably at least about 78), while the flexible material is a soft plastic (such as a urethane or silicone) having a Shore A hardness of about 40-100 (preferably about 40-94), a thickness on the trailing edge of about 0.2-0.4 inches, and a thickness on the leading edge of about 0.2-0.4 inches.
According to another aspect of the invention in the parent application a surfboard is provided having a top surface and a bottom surface, a front end (nose), and a rear end (tail). The surfboard includes at least one tail fin extending downwardly from the bottom surface adjacent the rear end. The fin comprises a rigid body element having a leading edge, and a trailing edge; and a flexible material covering disposed on the leading and trailing edges of the rigid body element, the covering material having sufficient thickness, softness and flexibility to minimize injury to a person impacted by a leading or trailing edge of the fin, and to be deflected by water pressure during surfing to provide a rudder action (anti-cavitation action) as a surfer shifts his or her weight on the top surface of the surfboard.
The surfboard according to the parent application has a centerline between the front and rear ends, and preferably has three fins. A first fin is provided closest to the tail and disposed on the centerline, with the second and third fins disposed further from the tail than the first fin and off the centerline. The second and third fins are disposed approximately the same distance from the tail as each other and approximately the same distance from the centerline and on opposite sides of it, and have flat inner side faces. The leading and trailing edges of the first fin are substantially coplanar with the center plane containing the centerline. The second and third fin leading and trailing edges are in planes which makes a slight angle (e.g. about 2.degree.-10.degree.) to the centerline, the leading edges being slightly closer to the centerline than the trailing edges. Also the center plane is substantially vertical when the board is in use, while the planes containing the leading and trailing edges of the second and third fins are slightly off vertical (e.g. about 2.degree. to 15.degree.).
The fins utilized according to the invention may be manufactured by a wide variety of techniques, including by: molding both the rigid and the flexible plastics together at the same time; injection molding the flexible plastic onto the rigid plastic once it has been formed (the preferred manner); or cutting and contouring sheets or strips of flexible material and adhesively connecting them to the edges of the rigid material.
The fins may be connected to the surfboard by primarily conventional techniques utilizing fiberglass rope and fiberglass cloth impregnated in resin, the fiberglass rope extending along all portions of the enlarged base of the rigid plastic element of the fin, while the fiberglass cloth extends up along the sides of the rigid plastic portion of the fins. The preferred manner of attaching the fin to the surfboard to ensure proper rigid connection of the fin to the bottom of the surfboard, while also ensuring that there is no damage to the flexible material comprises the steps of substantially sequentially: (a) Placing a protective material on the fin so that it substantially completely covers the flexible material of the fin, but only a small portion of the rigid body element. (b) Applying resin impregnated fiberglass rope or roving to the base of the fin, spaced from the flexible material, and the bottom of the surfboard. (c) Applying resin impregnated fiberglass cloth to the fin and the bottom surface of the surfboard so that the cloth substantially covers the fin. (d) Cutting away most of the fiberglass cloth exterior of the fin. (e) Abrading the fiberglass cloth off of the fin at areas thereof covering the flexible material and portions thereof covering the rigid body element where it is undesired, the protective material protecting the flexible material from significant damage during the abrading action. And, (f) removing the protective material from the fin so that the flexible material is exposed.
Step (a) is preferably practiced by placing a foil (e.g. aluminum) tape with pressure sensitive adhesive over the flexible material, and step (f) is practiced by pulling the tape from the fin. After step (f) any pressure sensitive adhesive adhering to the flexible material is removed with solvent. Mold release agent, such as pva, may be applied to the external surface of the protective material if necessary, although the surface of aluminum foil releases sufficiently so that a mold release agent is normally not necessary therewith.
Step (c) is preferably practiced by applying two to three layers of translucent fiberglass cloth, and step (e) is practiced by sanding with a power sander. Desirably the sides of the rigid body of the fins have a ridge formed thereon, and steps (d) through (f) are practiced to remove substantially all fiberglass cloth between the ridges and the leading and trailing edges, and step (e) is practiced using the ridges as guides during sanding. Steps (a) through (f) may be practiced for at least one other fin (e.g. for three fins total).
As seen above, it is highly desirable to protect the flexible material during the manufacture of the surfboard with the fin according to the present invention thereon. It has been found that if the flexible material is not sufficiently protected, especially during the sanding step, significant damage can be done thereto. One way that this can be avoided is to apply a protective material to the fin immediately after it is manufactured, and before it is sent to the surfboard manufacturer for incorporation into the surfboard.
According to another aspect of the present invention, a surfboard fin intermediate, used to make a final surfboard, is provided. The intermediate comprises the following elements: A rigid body element having a leading edge, a base, and a trailing edge. A flexible material covering disposed on the leading and trailing edges of the rigid body element, spaced from the base, the flexible material being soft enough to minimize injury to a person impacted by a leading or trailing edge of the fin, and being flexible enough to be deflected by water pressure during surfing to provide a rudder, anti-cavitation, action. And, a protective material having protective properties sufficient to protect the flexible material from damage during manufacturing processes, including sanding, readily removably secured to the flexible material and a small part of the body element to substantially completely cover the flexible material to protect it during manufacture of a surfboard with surfboard fin attached thereto.
Preferably the protective material comprises thin metallic sheet material deformed to bend over and cover the flexible material, most preferably a metal (aluminum) foil tape secured by pressure sensitive adhesive. The tape preferably has a thickness of about 4-9 mils, and has a width of about one-half inch to one inch (preferably 3/4-5/8 inch). Pva, or another mold release agent, may be applied to the external surface of the protective material if necessary to facilitate its release from the fiberglass cloth.
The fin rigid body element has first and second side faces and a substantially continuous ridge formed on each side face spaced from the flexible material, and a recessed side surface disposed within the perimeter of each of the ridges for receiving fiberglass cloth therein. The small part of the rigid body element to which the protective material is secured is outside the perimeters of the ridges.
According to yet another aspect of the present invention a surfboard, having top and bottom surfaces, a front end, and a rear end is provided. The surfboard also comprises: At least one fin extending downwardly from the bottom surface adjacent the rear end, the fin comprising: a rigid body element having a leading edge, a base, side faces, and a trailing edge; a flexible material selected from the group consisting essentially of rubbers, silicone, and urethanes disposed on the leading and trailing edges, spaced from the base, the thickness on the leading edge being about 0.2-0.4 inches, and the thickness on the trailing edge being about 0.2-0.4 inches; and a substantially continuous ridge extending outwardly from each of the side faces between the base and the flexible material. And, resin impregnated fiberglass holding the base and the side faces within the perimeter of the ridges to the bottom surface of the surfboard, to thereby rigidly hold the fin in position with respect to the surfboard.
It is the primary object of the present invention to provide a method of manufacture of a surfboard having a fin with enhanced safety and maneuverability characteristics, and to provide a fin intermediate particularly useful for that purpose. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.